1. Field of the Invention
This invention relates to catalytic hydrogenation of organic compounds containing carbonyl groups, and, more particularly, to the effective and rapid reduction of the carbonyl group to the corresponding hydroxy group, sometimes even very selectively in the presence of a carbon-to-carbon unsaturated group in the same compound.
2. Description of the Prior Art
Many hydrogenation catalysts are known in the art for the reduction of carbonyl functional groups in organic compounds. Several are available, too, for selectively reducing the carbonyl group to the corresponding hydroxy group in the presence of a carbon-to-carbon unsaturated group in the same compound. Such catalysts are described in detail, for example, in Catalytic Hydrogenation by R. L. Augustine M. Dekker Inc., N. Y. (1965). As disclosed in this book, a copper-chromium oxide ("copper chromite") catalyst will promote the hydrogenation of an aldehyde group in preference to a generally more reactive vinyl group. However, such selective hydrogenations generally require extreme pressure (3000 psi) and high temperature (140.degree.-160.degree. C.) conditions. A related catalyst, zinc-chromium oxide, makes use of the ability of zinc ions to inhibit the hydrogenation of double bonds for conversion of unsaturated esters to unsaturated alcohols, but also necessitates high pressures and temperatures.
Conventional Raney nickel catalysts, which have been used for some time as hydrogenation catalysts, also are not entirely satisfactory for reduction of carbonyl groups, because of their relative inactivity.
Accordingly, it is an object of the present invention to provide an improved method for reducing carbonyl groups in organic compounds, and, particularly to a method for selectively hydrogenating carbonyl groups, sometimes even in the presence of carbon-to-carbon unsaturated groups. A specific object herein is to provide such a method which can be carried out effectively and rapidly at low pressures and temperatures, in an economical process, using an inexpensive catalyst, whereby the desired product is obtained in high yield with a minimum of by-products.